This invention relates to the manufacture of 1,3-propanediol. In one aspect, the invention relates to an improved catalyst for hydrogenating 3-hydroxypropanal to 1,3-propanediol which exhibits prolonged catalyst life in the hydrogenation reaction environment. In a further aspect, the invention relates to an improved process for preparing 1,3-propanediol from 3-hydroxypropanal.
1,3-propanediol, a chemical intermediate in the preparation of polyesters, can be prepared by hydrogenation of 3-hydroxypropanal in aqueous solution. Selective hydrogenation of 3-hydroxypropanal to 1,3-propanediol is complicated by the high reactivity of 3-hydroxypropanal and the relatively low solubility of hydrogen in aqueous solution.
Hydrogenation in a trickle-bed configuration is favored by small catalyst particle size. However, catalyst crush strength is significantly diminished with reduced catalyst particle size. A common approach to increasing the crush strength of nickel-based bulk catalysts is to increase the amount of calcium in the binder. However, in the aqueous hydrogenation environment, calcium and other soluble binder components are quickly leached from the catalyst. This has two negative effects on the synthesis process. First, as the water is evaporatively separated from the 1,3-propanediol, the leached binder material is deposited in the evaporation column, resulting in down-time and equipment clean-up costs. Second, the removal of these soluble components from the particulate catalyst lowers the crush strength of the catalyst, resulting in less efficient flow-through in the catalyst bed as areas of catalyst collapse and eventually plug the bed.
It is therefore an object of the invention to provide a catalyst and process particularly designed for the hydrogenation of 3-hydroxypropanal to 1,3-propanediol in aqueous solution. In one embodiment, it is an object of the invention to provide a catalyst for the hydrogenation of 3-hydroxypropanal having reduced leachable content without significant reduction of crush strength in the reaction environment.
According to the invention, a solid catalyst composition is provided containing an active nickel component in which the nickel constitutes from about 25 to about 60 wt % of the catalyst composition; a molybdenum component in which the molybdenum constitutes from about 5 to about 20 wt % of the catalyst composition; and a binder component comprising from about 10 to about 50 wt % of a binder material selected from at least one of oxides of silicon and silicates and oxides of zirconium, aluminum, zinc and calcium, with the aluminum, calcium and zinc each present in the catalyst composition in an amount no greater than 2 wt %, preferably 0-1 wt %.
Further according to the invention, a process for preparing 1,3-propanediol is provided comprising contacting an aqueous solution of 3-hydroxypropanal under hydrogenation conditions with a catalyst containing an active nickel component in which the nickel constitutes from about 25 to about 60 wt % of the catalyst composition; a molybdenum component in which the molybdenum constitutes from about 5 to about 20 wt % of the catalyst composition; and a binder component comprising from about 10 to about 50 wt % of a binder material selected from at least one of silicates and oxides of zirconium, aluminum, zinc and calcium, with the aluminum, calcium and zinc each present in the catalyst composition in an amount no greater than 2 wt %, preferably 0-1 wt %.
The use of the described catalyst in the hydrogenation of aqueous 3-hydroxypropanal permits the production of 1,3-propanediol in high yields with reduced downtime from the effects of the use of soluble binder materials.